The present invention relates generally to semiconductors, and more specifically the invention pertains to a bridge-chip connector for interconnecting two semiconductor devices that contain densely packed control points.
The trend in integrated circuit manufacture is toward greater integration of functions on a single chip. This results in more gates on the chips and higher input/output (I/O) pin counts. I/O requirements of over 200 leads on a single chip indicate a general trend involving the addition of increasingly numerous leads, which makes semiconductor chip interconnection more difficult. Electronic circuit systems are typically made by defining complex integrated circuit structures on semiconductor chips, bonding the chips to circuit package substrates, and in turn bonding the packages to printed circuit boards. The most common bonding technique is wire bonding, in which an instrument (a thermode) bonds wire to a bonding pad of one element, such as a chip, and then pulls the wire and makes a bond on a bonding pad of a second element so as to form a self-supporting wire bridge between the two bonding pads.
The task of interconnecting semiconductor chips to each other is alleviated, to some extent, by the systems disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 4,843,191 issued to Thomas;
U.S. Pat. No. 4,531,285 issued to Lucas; and
U.S. Pat. No. 4,378,902 issued to Fedak.
The patent to Lucas discloses bonding the lead frame material to a thin insulating film and forming the leads, then the film is removed where connections are to be made. The lead material is then plated and formed to provide stress relief in the package to board connection. The lead frame is then attached to the package and board. The patent to Thomas discloses usage of dielectric tape to cover a row of bonding pad connectors so that an additional row of bonding pad connectors can be used. The dielectric tape is electrically insulating. The patent to Fedak discloses a wall or spacer to prevent wire connections from shorting out.
The above-cited Thomas reference shows a system of parallel conductors fixed on dielectric tape. The present invention makes use of a rigid bridge base that can be wedged between fixed semiconductor chips to hold the conductive leads in a rigid fixed position over adjacent contact pads. The advantage of a rigid base is that it avoids one potential problem of dielectric tape. More specifically, dielectric tape is flexible, and movement of the tape (by jarring the device etc.) can displace the electrical connectors so that they disconnect from the correct contact pads, and perhaps short out. The thin insulating film used in the above-cited Lucas reference also appears to have a potential problem with displacement due to flexibility. The Lucas solution to the displacement problem is to add a strip of brace material to one end of the parallel leads. While this may solve the problem, a more elegant solution is provided by the present invention in using a rigid central insulating bridge brace with a plurality of parallel conductive beam leads fixed to its top surface.
While the above-cited references are helpful, the need remains to provide a method of interconnecting semiconductor chips which have densely parked control points. The present invention is intended to satisfy that need.